Kidnapping a process’s pwd and root

This evening I wrote a chunk of code that, given a PID, goes and does the chdir() and chroot() calls on it to a given directory. That process suddenly finds itself isolated while it’s running. It’s kind of like pulling the carpet pulled out from under it, but so quickly it doesn’t notice.

In other words, I’m kidnapping a process, and stuffing it into a chroot.

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Added “ps” extras feature to tpe-lkm

Since I already had my hands in the tpe-lkm code yesterday, I decided to spend my lunch break coding a feature I’ve been meaning to add in for a while now.

I added a new ps extras feature. Since it doesn’t have to do with the “trusted path”, I added it to the “extras” in the configuration. It’s similar to grsecurity’s “Proc restrictions” where “the permissions of the /proc filesystem will be altered to enhance system security and privacy”. Basically, non-root users won’t be able to view the processes they don’t own.

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tpe-lkm DoS condition fixed

I have committed a fix to the tpe-lkm project that fixes a DoS condition I previously noted.

It also introduces a new sysctl entry, log_max, as to prevent logs from getting filled up horizontally. I set the default to 50, seemed high enough without giving an attacker too much leverage on spewing junk into the log file should they get the chance, yet low enough to catch the full process tree of you basic exploit attempt.

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Recursive function causes DoS in tpe-lkm

I’ve discovered my first denial-of-service bug in the linux kernel. I’m a bit teary eyed, not because the bug was in my own code, but it marks the first bug I’ve found in linux kernel code.

Not worth of a CVE or anything, because I still haven’t declared the code stable, and I don’t imagine many people use this thing just yet. But in the interest of full disclosure, here is information about the bug.

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My own private protest

I’ve noticed that I have started to put on some weight (again). The last time my weight started to go up, I counted calories, and managed to get the weight down and stable for a little over a year. This time, however, I’m going to do something different about it.

In the spirit of the various “Occupy” protests lately, I’ve decided to start my own private protest:

Occupy Kitchen

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nagios snmp memory and swap plugin

Since I’m on a nagios and snmp kick this week, here’s a nagios snmp plugin I wrote to check memory and swap. The real difference between this script and the standard nagios plugins for memory / swap, is it takes buffered and cached memory into account, giving the real % free.

Here is the script, and it’s usage is pretty simple:

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A nagios snmp plugin that obeys snmp.conf

So there is a currently unresolved issue with the check_snmp nagios plugin where it doesn’t use the snmp.conf file. I use v3 of the protocol, and don’t want to have to put the big long string everywhere in the nagios configuration file:

define command{
  command_name check_snmp_cpu
  command_line $USER1$/check_snmp -H $HOSTADDRESS$ -w 2 -c 4 -u "cpu" -P 3 -L authPriv -a MD5 -U snmpmonitor -A "have a look at what I have to offer" -x des -X "have a look at what I have to offer" -o .

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